Ever more stringent regulations regarding permissible pollutant emissions by motor vehicles fitted with internal combustion engines make it necessary to keep the pollutant emissions as low as possible during operation of the internal combustion engine. One of the ways in which this can be done is by reducing the emissions which occur during the combustion of the air/fuel mixture in the relevant cylinder of the internal combustion engine. Another is to use exhaust gas handling systems in internal combustion engines which convert the emissions which are generated during the combustion process of the air/fuel mixture in the relevant cylinder into harmless substances. Catalyzers are used for this purpose which convert carbon monoxide, hydrocarbons and nitrous oxide into harmless substances. Both the explicit influencing of the generation of the pollutant emissions during the combustion and also the conversion of the pollutant components with a high level of efficiency by an exhaust gas catalyzer require a very precisely set air/fuel ratio in the respective cylinder.
A device for an internal combustion engine with an exhaust gas catalyzer in an exhaust gas tract is known from SAE International Publication “A Metal Substrate with Integrated Oxygen Sensor; Functionality and Influence on Air/Fuel Ratio Control”, Mats Laurell et al., SAE 2003-010818. A linear Lambda sensor is arranged upstream from the exhaust gas catalyzer in the exhaust gas tract. In addition a first and a second binary lambda probe are arranged in the exhaust gas catalyzer. The binary Lambda probe is used for trimming the probe signal of the linear Lambda sensor. The measuring signal of the linear Lambda sensor thus trimmed is the regulating variable of a Lambda controller.
Closed-loop Lambda control with a linear Lambda probe which is arranged upstream from an exhaust gas catalyzer and a binary Lambda probe which is arranged downstream of the exhaust gas catalyzer is known from the German textbook, “Handbuch Verbrennungsmotor”, published by Richard von Basshuysen, Fred Schäfer, 2nd edition, Vieweg & Sohn Verlagsgesellschaft mbH, June 2002, Pages 526-528. A Lambda setpoint value is filtered by means of a filter which takes account of gas delay times and the sensor behavior. The Lambda setpoint value filtered in this way is the closed-loop control variable of a PII2D Lambda controller, for which the manipulated variable is an injection volume correction.